In devices for continuous or semi-continuous casting, it is a well-known fact to brake the flow of metal in a mould by applying one or more magnetic fields to the molten metal. A plurality of different brake configurations have been proposed. Normally, electromagnetic brakes are used, that is brakes that comprise one or more magnetic cores and one or more winding around the latter.
The theory behind braking by means of magnetic fields is based on the fact that a current is induced in the molten metal thanks to the presence of the magnetic fields in accordance with i=v×B, where i is the induced current, v is the velocity of the molten metal, and B is the size of the magnetic field. A force f=i×B is obtained in the molten metal. According to well known principles, the force f has a direction opposite to the direction of the velocity vector v, and therefore it has braking effect on the flow.
By moulds that have broad sides and short sides, electromagnetic brakes are normally arranged along opposite broad sides. In that way, a magnetic field that covers generally the whole width of the melt can be obtained, However, the induced current in a region adjacent to the short sides will not be able to become closed, but will depart from the molten metal through the shorts side. This, in its turn, results in the braking force f not being obtained in this region.